Quick Links

PS4 may be better than first thought

Theres an interesting thread over on Neogaf that discusses the PS4 having Uniform memory access. This is different than unified memory. I'm not totally sure of the tech but it goes something like this.

Unified memory is where both the CPU and the GPU access the same memory. However, when the CPU needs to do some work on the data being used by the GPU it needs to copy the data, do the calculations and then copy it back once done.

Wit Uniform memory, both the CPU and the GPU can read and write to exactly the same memory area meaning that no additional copying needs to be done.

NOTE: I may not have got this exactly right but close enough for these purposes.

AMD claim that this could give the PS4 a significant performance boost and also improved textures

Not entirely. Firstly, games for the PS4 would be able to run at higher FPS with out any recoding. Secondly it seems that a simple higher res texture pack could improve the look of a game at little or no extra cost to the developer. I guess it's also possible that the I proved performance could also be utilised directly by the console to implement post processing effects independent of the games.

As I said in my OP, it all depends upon the performance improvements realised in the real world. If its just a 10% improvement then I would expect extra FPS and maybe some slightly better textures. If its 50% improvement then I would expect some real tangible enhancements.

I'm still trying to work out whether the PS4 will have any *killer* features which make it a must buy or whether it will be an evolution of the current set up. I've always been a late adopter, but from my perspective:

PS1 - Revolution in (console) gaming in terms of graphics and game play

PS2 - A decent evolution in gaming combined with a DVD player which was a revolution in video playback.

PS3 - Another reasonable jump in gaming (though IMO not as much as with 1 & 2), BluRay was a strong addition (though not revolutionary) however the media center set up was the key feature and worked extremely well with the evolution of downloading and streaming media.

There would be nothing wrong with the PS4 being a sold development in all areas, I'm just wonder whether it will have anything that I couldn't like without for the next year or so.

They've taken a lot of the ideas they added on later to the PS3 and are now making them the core features. Like the new UI featuring more online content being at the heart of the console instead of having to go into the PS Store to see it.

ps4 will have galaki or something too,
that could a potentially awesome feature

imagine being able to play demos/games without even having to download them first ,
i believe they use the same tech also so if your stuck on a game , you can ask a friend to hop into your game and do it for you

potentially means you can play any game from ps1/ps2/ps3/ps4 without needing disk or download, or updates etc

AMD has provided a few more details about its upcoming Heterogeneous System architecture (HSA), revealing the name of the unified memory system it will be using: Heterogeneous Unified Memory Access (hUMA).

HSA is AMD's big vision for its future APUs. Like its existing APUs, HSA chips will feature a CPU and GPU on one piece of silicon but the big innovation with HSA is that the two units will now share memory directly, thus hUMA.

On current AMD and Intel APUs the CPU and GPU have separate memory blocks. So for the GPU to do some processing it requires the appropriate data to be copied from the CPU memory to the GPU memory, and back again once the processing is finished. This creates a severe bottleneck in performance and greatly increases complexity for programmers.

By unifying the two blocks of memory and allowing the CPU and GPU to directly access the same data the performance overhead of copying all the data is eliminated and programming complexity is greatly reduced.

AMD highlighted what it sees as the top ten benefits of HSA in a recent presentation:

Much easier for programmers
No need for special APIs
Move CPU multi-core algorithms to the GPU without recoding for absence of coherency
Allow finer grained data sharing than software coherency
Implement coherency once in hardware, rather than N times in different software stacks
Prevent hard to debug errors in application software
Operating systems prefer hardware coherency - they do not want the bug reports to the platform
Probe filters and directories will maintain power efficiency
Full coherency opens the doors to single source, native and managed code programming for heterogeneous platforms
Optimal architecture for heterogeneous computing on APUs and SOCs.

"Although both upcoming game consoles Xbox One and PlayStation 4 are based on AMD hardware, only PlayStation 4 incorporates hUMA [Heterogeneous Uniform Memory Access] for supporting a shared memory space. This was explained by AMD's Senior Product Marketing Manager Marc Diana to c't [big German IT magazine] at gamescom"

this from gaf:

"
On a classical system you have a RAM pool and a VRAM pool that are physically speperated. Copying data from one pool to the other creates latency. The GPU is very good ad hiding latency. What it needs most is high bandwidth. The CPU on the other hand is extremely sensitive to latency. The CPU needs extremely low latency to work efficiently. Copying data from the RAM (CPU) to the VRAM (GPU) creates latency, but that's okay for the GPU. Copying data from RAM (CPU) to VRAM (GPU) and back to the RAM (CPU) creates even more latency. It's too much for the CPU. The copying alone takes longer than the computation wich makes this roundtrip highly ineffective.

Xbox360 and older APUs have a unified RAM. This means that the RAM is no longer physically seperated, but even though it's the same RAM chips, the system still distincts between memory partition for the differenct processors. You still need to copy the data between CPU partition and GPU partition, but this will be much more efficient than copying it between physically seperated pools. But it's still too much latency for a CPU, GPU, CPU roundtrip.

PS4 will have hUMA wich means that you no longer need a distinction between CPU partition and GPU partition. Both processors can use the same pieces of data at the same time. You don't need to copy stuff and this allows for completely new algorithms that utilize CPU and GPU at the same time. This is interesting since a GPU is very strong, but extremely dumb. A CPU is extremely smart, but very weak. Since you can utilize both processors at the same time for a single task you have a system that is extremely smart and extremely strong at the same time.

It will allow for an extreme boost for many, many algorithms and parts of algorithms. On top of that it will allow for completely new classes of algorithms. This is a game changer."

Well saying that Kabini doesn't support hUMA doesn't mean much because it doesn't support GDDR5 either! And it only has quad-core CPU, and hardly any GPU cores.

Sony are members of the HSA Foundation, for what it's worth.

I know it's a very confusing situation. Nothing that anyone says 100% confirms or 100% denies the clams. So far I've heard that PS4 has it, Both have it and neither have it. I've yet to hear that Xbox has it and PS4 doesn't. So maybe that's the true statement

I know some still state that they believe the initial article and the quote from the second doesn't explicitly deny the first but for now I think I'm going to have to assume no huma until explicitly confirmed by AMD, Sony or an in depth technical review of the system.